JPS61226916A - Inversion of polycrystal semiconductor material to monocrystal semiconductor material - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a layer structure having a polycrystalline or amorphous semiconductor material layer between a first electrically insulating layer and a covering layer on a substrate; A crystalline or amorphous semiconductor material is irradiated by a radiation source that provides practically monochromatic electromagnetic radiation that is practically completely transparent at least at room temperature, the energy being transferred to the polycrystalline or amorphous semiconductor material at least It relates to a method for converting a polycrystalline or amorphous semiconductor material into an essentially monocrystalline semiconductor material by heating said layer structure sufficiently to partially convert it into a monocrystalline semiconductor material. be. The invention also relates to a device provided with a single crystal semiconductor material produced by such a method.

Methods of the above-mentioned type can be used advantageously, for example, in the production of so-called three-dimensional integrated circuits, in which the underlying circuits, such as memory matrix registers, multiplexers, etc., are used for further operation. After applying the insulating layer for protection against influences, it is necessary to provide this insulating layer again with short crystalline regions for transistors or other circuit elements. Another field of use is, for example, the production of single-crystal semiconductor materials on insulating substrates to form optoelectronic components.

The method described at the beginning is disclosed in Japanese Patent Application Laid-Open No. 57-124423.
It is known from the issue. By the method described herein, carbon is added to a polycrystalline silicon layer located between two SiO□ layers.
The polycrystalline silicon layer is recrystallized by irradiation with electromagnetic radiation emitted by an O□ laser. The wavelength of this radiation is approximately 10 μm, whereas polycrystalline silicon is almost completely transparent at room temperature, so virtually no energy is absorbed due to recrystallization.

It is therefore usually preferable to choose a radiation source with a wavelength such that the maximum possible amount of energy is absorbed by the semiconductor material, for example an argon ion laser being preferred in the case of polycrystalline silicon. On the other hand, e.g. CO2
The use of lasers has various advantages over argon ion lasers, apart from the low absorption in polycrystalline silicon. Firstly, the emission is more stable and therefore the intensity of the emitted radiation is more constant. Furthermore, C
The output power of the Ot laser is significantly greater than that of the argon ion laser, and the optical power is even greater. Moreover, the price is even more favorable. Furthermore, due to the large output, CO. Several beams can be generated by the laser at the same time, which may be advantageous for certain applications.

The present invention uses radiation that is virtually completely transparent to polycrystalline semiconductor materials, yet absorbs enough radiation to rapidly heat the semiconductor material to a temperature where nearly complete absorption is achieved. The objective is to provide a method for allowing this to occur in a layered structure.

According to the invention, at least 4% of the energy delivered to the layer structure by the radiation source is absorbed into the layer structure and at most 60% of said energy is delivered to the underlying substrate. One of the above objectives is achieved by a method of converting a crystalline semiconductor into a single crystal semiconductor material.

The invention achieves the above object by a suitable construction of the layer structure, in particular by mutually adapting the thicknesses of the various layers so that the first electrically insulating layer and the covering layer are heated quickly. Based on what you find achievable. As a result, the intervening semiconductor material is also heated relatively quickly to a temperature where it practically behaves as a metal and absorbs a relatively large portion of the radiation. If desired, the whole can be heated more rapidly by heating elements, possibly by temporary heating.

In a preferred embodiment of the method according to the invention, in the layer structure an even number, n
and n' are odd numbers, λ1. λ■ and λ1 are the wavelengths of electromagnetic radiation in the covering layer, the polycrystalline semiconductor material layer and the first electrically insulating layer, respectively.

With such a layer structure, an absorption rate of 8% can be achieved at room temperature, and only 32% of the radiant energy is delivered to the underlying substrate. JP-A-57-12442
It is true that in the structure disclosed in No. 3, the thickness of the covering layer is not indicated, but if this layer is of normal thickness, a proportion greater than about 60% of the electromagnetic radiation will be emitted. If applied to the underlying substrate and the covering layer is of suitable thickness, the absorption in the layer structure is very low (approximately 1%).

The invention will now be explained by way of example with reference to the drawings.

FIG. 1 shows a device 1 having a layer structure 2 on a substrate 10. FIG. The substrate 10 is, for example, a silicon object, for example,
A finished semiconductor circuit can be provided. Alternatively, the substrate 10 is an electrically insulating material (glass or sapphire).
It can be composed of

In this example, the layer structure 2 comprises a first silicon oxide layer 3 with a thickness of about 1.25 μm and a polycrystalline silicon layer 4 with a thickness of about 0.77 μl, this thickness of layer 3 being emitted by a CO□ laser. The wavelength of the radiation (approximately 10.6 μm in vacuum) in silicon dioxide corresponds to approximately λIII. This layer structure 2 furthermore comprises a silicon dioxide covering layer 5 with a thickness of approximately 2.5/f, the thickness of which limits the wavelength of the radiation emitted by the CO2 laser to the silicon dioxide by λ1.
This corresponds to approximately 1λ1. If desired, thin layers, for example thin layers of silicon nitride (not shown), can be placed between the various layers mentioned above, and these thin films can act as diffusion suppressants and further Ensure good wetting or satisfactory thermal and mechanical compatibility.

Middle layer and layer5. Middle layer and layer 4. and interlayers and layers. In some applications, for example when producing so-called three-dimensional IC1s, i.e. a plurality of polycrystalline silicon layers deposited on an electrically insulating substrate, N4 is completely or partially applied to monocrystalline silicon. It is desirable to be able to form active devices therein, such as transistors or other circuit elements.

According to the invention, the layer structure 2 is irradiated with monochromatic radiation emitted by a CO□ laser for this purpose. However, since at room temperature layer 4 is almost completely transparent to such radiation, no special steps are necessary, although the desired heating to the melting point and subsequent recrystallization into single crystal silicon requires a large amount of energy and a long time. is necessary. A large portion of the unabsorbed energy may further penetrate into the substrate 10 and cause damage there; if a circuit has already been formed, the conductor tones may be melted in whole or in part by heating. The increased temperature may also cause out-diffusion in the semiconductor region.

However, in the first example, the illustrated layer structure absorbs enough energy in layers 3 and 5 to rapidly heat polycrystalline silicon layer 4 to a temperature of practically 800°C. At this temperature (and above), silicon exhibits essentially metallic properties for the relevant wavelengths and almost all of the energy is absorbed into layer 4. layer structure 2
Such rapid heating is achieved in that approximately 4% of the energy of the radiation 6 is absorbed into the layered body 2 (at ambient temperature). The heating process can be accelerated by heating the device l beforehand, if desired, by other means, for example by placing the whole on a substrate heater. Of course, the temperature of the substrate 10 must not be raised to such an extent that the above-mentioned damage occurs.

In the layered structure 2 of FIG. 1, the thicknesses of layers 3, 4 and 5 are selected in close relation to the wavelength of the radiation used, although some variation in these thicknesses is allowed. Although the absorption rate is sufficiently large (4% or more), the transmittance of the radiation 6, the secondary substrate 1
The condition is met that the part of the energy that reaches 0 still remains at an acceptable level (<60%).

This will be explained with reference to FIG. FIG. 2 shows the absorption (curve 7), transmittance (curve 8) and reflectance (curve 9) obtained at room temperature for radiation 6 with a wavelength of 10.6 μm for the layered structure 2 and the interlayer 4. The relationship between the thickness of From FIG. 2, it can be seen that the thickness of polycrystalline silicon is 0.2λ and 0.2λ.
3λ1, the transmittance is low (<45
%) and the absorption rate is found to be sufficiently large.

The absorption was still above 4% and the transmission was acceptably high (60%). Polycrystalline silicon layers 4 and 540
A thin layer (approximately 10-20 nm) of silicon nitride, for example, can be provided between each of the two layers 3 and 5. These layers serve, on the one hand, to provide satisfactory adhesion between the layers and, on the other hand, to optimize the temperature distribution in the layer structure or to neutralize mechanical stresses. Moreover, silicon nitride has satisfactory etch selectivity and chemical inertness properties.

In a broader sense, the conditions described above (absorption>nI 4% and transmittance <60%) are approximately -24% for the top layer.
This is satisfied when the thickness of 噸 (where m is an even number) is selected, and when the thickness of λ111 (where n and n' are each an odd number) is selected.

Finally, FIG. 3 shows an enlarged view of the multilayer structure 2 with an additional polycrystalline silicon layer 12 on the underside, which layer is separated from the substrate 10 by an additional silicon dioxide electrically insulating layer 11.

The polycrystalline silicon layer 12 can be heavily doped, for example, and forms part of a wiring pattern connecting the circuit elements formed in the substrate 10 and the semiconductor elements to be provided in the monocrystalline silicon to be produced. be able to. Also in this structure, if the thicknesses of layers 3, 4.degree. layer 1
Further optimization is achieved by selecting thicknesses of approximately 1.25 μm and 0.77 μm for 1 and 12, respectively.

In a broader sense, layers 11 and 12 are chosen to represent the wavelength of electromagnetic radiation in the additional electrically insulating layer and the additional layer of polycrystalline semiconductor material.

Of course, the present invention is not limited to the examples described here, and those skilled in the art can make various changes without departing from the scope of the present invention. For example, in the example described above, a CO laser or a neodymium-doped YAG laser can be used instead of a CO□ laser. Additionally, other semiconductor materials, such as G'aAs, can be used in optoelectronic applications, or a combination of GaAs and silicon can be used in optoelectronic applications, or a combination of GaAs and silicon can be used in one semiconductor. It can be selected in the device.

If required, other lasers with wavelengths that are virtually completely transparent to GaAs, such as neodymium-doped YAG
Lasers can be selected. Silicon monoxide can be used instead of silicon dioxide both in the intermediate layer and in the covering layer. Furthermore, amorphous silicon can be chosen as layer 4.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an example of a layer structure suitable for use in the method of the invention; FIG. absorption rate,
A graph showing the relationship between transmittance and reflectance, respectively. FIG. 3 is a cross-sectional view of an example of a multilayer structure suitable for use in the method of the present invention. I... Device 2 having layer structure 2 on substrate 10.
・Layer structure 3 ・Silicon oxide layer 4・
... Polycrystalline silicon layer 5 ... Silicon dioxide coating layer 6
...Monochromatic radiation (electromagnetic radiation)

Claims (1)

[Claims] 1. A layer structure having a polycrystalline or amorphous semiconductor material layer between a first electrical insulating layer and a covering layer is provided on a substrate, and the layer structure is irradiating the semiconductor material by a radiation source that provides practically monochromatic electromagnetic radiation that is practically completely transparent at least at room temperature, the energy being transferred at least partially by the polycrystalline or amorphous semiconductor material. converting a polycrystalline or amorphous semiconductor material into an effectively single-crystal semiconductor material by heating the layer structure sufficiently to convert it into a single-crystal semiconductor material; A polycrystalline semiconductor material characterized in that at least 4% of the energy supplied to the layer structure is absorbed into the layer structure and at most 60% of the energy is supplied to the underlying substrate. How to convert it into materials. 2. In the layered structure, the covering layer is actually (m/
4).λ^ I and said polycrystalline or amorphous semiconductor material layer and said electrically insulating layer have a thickness of (n/4).λ^ II and (n'/4).λ^ in practice, respectively. I
II, where m is an even number, n and n
' is an odd number, and λ^I, λ^II and λ^III are the wavelengths of electromagnetic radiation in the covering layer, the polycrystalline or amorphous semiconductor material layer and the first electrically insulating layer, respectively. The method described in Section 1. 3. The layer structure has between the first electrically insulating layer and the substrate at least one double layer consisting of an additional electrically insulating layer and an additional layer of polycrystalline semiconductor material present thereon. A method according to claim 1 or 2. 4. The additional insulating layer and the additional polycrystalline semiconductor material layer have approximately (n″/4)·λ^IV and (n′
''/4)・λ^V, and in the above formula, n''
and n''' are even numbers, and λ^IV and λ^V are the wavelengths of electromagnetic radiation in said additional insulating layer and said additional layer of polycrystalline semiconductor material, respectively. 5. The method according to any one of claims 1 to 4, wherein the electromagnetic radiation is emitted from a CO_2 laser, a CO laser, or a Nd-YAG laser. 6. Claim 1 in which the substrate is heated to a high temperature in advance
5. The method according to any one of items 5 to 5. 7. The method according to any one of claims 1 to 6, wherein the substrate comprises a semiconductor body, and circuit elements are formed on the semiconductor body. 8. In order to improve mutual compatibility, at least one intermediate layer is provided between the polycrystalline semiconductor material and one or more other layers in the layer structure. The method described in any one of Section 7.